Radon

BeschreibungRadon, Rn, is a gaseous radioactive element from the noble gases in family eight on the periodic table. There are 18 radioactive isotopes of radon, all of which have short half-lives. For example, radon 222 has a half-life of 3.8 days. Radon is a colorless gas that is soluble in water. It can be condensed to a colorless transparent liquid and to an opaque, glowing solid. Radon is the heaviest gas known, with a density of 9.72 g/L at 32°F.

OccurrenceRadon’s source is a step in the transmutation of several elements: uranium → thorium →radium → radon → polonium → lead. (There are a number of intermediate decay productsand steps involved in this process.) Radon-222 forms and collects just a few inches below thesurface of the ground and is often found in trapped pockets of air. It escapes through poroussoils and crevices.

VerwendenRadon’s main use is as a short-lived source of radioactivity for medical purposes. It iscollected from the decay of radium as a gas and sealed in small glass capsules that are theninserted at the site of the cancer. It is also used to trace leaks in gas and liquid pipelines and tomeasure their rate of flow. The rate at which radon gas escapes from the Earth is one measurementthat helps scientists predict earthquakes.

DefinitionA colorless monatomic radioactive element of the rare-gas group, now known to form unstable compounds. It has 19 short-lived radioisotopes; the most stable, radon-222, is a decay product of radium-226 and itself disintegrates into an isotope of polonium with a half-life of 3.82 days. 222Rn is sometimes used in radiotherapy. Radon occurs in uranium mines and is also detectable in houses built in certain areas of the country. Symbol: Rn; m.p. –71°C; b.p. –61.8°C; d. 9.73 kg m–3 (0°C); p.n. 86.